I study the properties and outcomes of stellar mergers by performing three dimensional hydrodynamic simulations using the brand-new adaptive mesh refinement code Octo-Tiger. Thanks to its unique techniques for solving the hydrodynamic equations and gravity, Octo-Tiger conserves to an excellent precision energy, momentum, and most importantly for binary simulations, angular momentum. In addition, by using state-of-the-art techniques for its parallelization, Octo-Tiger can be run and scale to a very large number of cores and on various different architectures, reducing the running time by several factors. I showcased results of several different astrophysical binaries, where the two stars are comparable in size like double white dwarf mergers or a contact binary of two main-sequence stars. In addition, I describe a recent ongoing project of a red super giant star interacting with a companion much smaller in size main-sequence star and present the challenges in modeling such systems. As the significance of binary interactions and stellar mergers on massive stellar evolution and their environments is highlighted by both observations and theoretical studies over the recent years, there is a need for a better understanding of stellar mergers and their outcomes.